I may be a grasping, clutching, scraping, clinking, clanking, covetous old sinner, but I don't understand why someone would give a significant portion of their own tips to the wait staff, other than out of pure charity. After all, they don't give a portion of their tips to you, do they? and generally speaking, they're probably going to walk out with more money in their pockets than you are (after you've paid your bar bill!)

Don't get me wrong; I'll tip the staff in proportion to my bill and their service, but I don't see any relationship between that and what someone may have given me for singing their mother's favourite song (Danny Boy). Am I missing something here? I mean that honestly; I'm not trying to put anyone down, I'm just curious as to the rationale behind what seems to me an odd practice.